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"having fun" and encapsulated stains w/ cd and se

updated thu 31 jul 97


Ric Swenson on thu 17 jul 97

John, et al,

I read this message and picked up a copy of CERAMIC INDUSTRY to see if I
could find someone to ask about encapsulated stains containing Cadmium and
/ or Selenium.

In the search, I came across some phone numbers that might be of
interest...Depending on where you live, glaze colors can be bought from a
number of suppliers

Laguna Clay 800 452-4862
Continental Clay 800 432-2529
Minnesota Clay 800 252-9872
Bailey Clay 800 431-6067

Some carry encapsulated stains...some do not. Others that were helpful in
my research were:
Fusion Ceramics (frits) 330 627-2191
Kentucky -Tennessee Clay Co tech line 800 458-7378
Mason Colors 330-385-4400

Now to the MEAT of the message....

Degussa is a joint venture with Drakenfeld Color....NOW called "CERDEC, Corp."
You can reach a nice technical person called Rob Wilson at 412 229-5622
or email at

His advice was NOT to ball mill the encapsulated stains...but to use a low
or high shear mixer. The Zirconia encapsulation around the Cadmium can be
fractured, which will make the 1% of Cd in the mix more available to
leaching in foodstuffs.

They have a brochure...out of stock at the moment....unfortunately....but I
will get one and try to pass on info when I get it....or you can call Rob
and ask for a brochure to be sent directly to you.

I am working on the Gerstley Borate "situation" at 11 ! (HA)

Hope this helps.


>----------------------------Original message----------------------------
>My advice is ignore these restrictions (unless someone else here
>has reasons otherwise) & just test the red in some bases you like.
>As always - the definition of what WORKS is highly personal,
>idiosyncratic & fun. So go have some.
>Oops...... just gotta say something about this one .
>I don't know about all the particulars that the manufacturer has to say
>about their new encapsulated product, but that is pretty easy to check.....
>call them and double check.
>However, with handling a material like Cadmium in a glaze, it might just be
>a good idea to follow thier recommendations, particularly if the glaze is
>intended for functional surfaces. I may be wrong (probably am), but in the
>wrong base batch it MIGHT be possible that the encapsulation of the Cd in
>the Zr silicate could become "broken"or eroded ..... allowing the Cd to be
>"released" into the batch in general during the melt. Then the leaching
>(and fuming) of Cd might again be a concern again (along with losing the
>It is one thing to "ignore the manufacturers' recommendations" when using
>something pretty non-toxic, maybe like iron. It is another when it is
>something like Cd.
>Also the term "what works" is very nebulous....... it might work visually,
>but does it "work" chemically? For functional work, it has to be sucessful
>in both categories.
>Anyone really up on these encapsulated stains? I want to know more. Can
>the encapsulation be easily "ruptured", or is this stuff basically
>John Baymore
>River Bend Pottery
>22 Riverbend Way
>Wilton, NH 03086 USA

Ric Swenson, Bennington College, Route 67 -A, Bennington, Vermont 05201-6001
802 442-5401 x 262 vox x 237 fax or dedicated fax 802 442-6164